A series of MOFs based on a tricarboxylic acid and various N-donor ligands: syntheses, structures, and properties

Eight highly connected metal-organic frameworks (MOFs) based on flexible tricarboxylate ligands, namely, Na[Zn-5(L)(2)(mu(3)-OH)(5)] (1), (HTEA)[Zn-3(L)(2)(mu(3)-OH)]center dot 0.25H(2)O (2), [Zn-3(L)(2)(BIME)(H2O)(2)] (3), [Cd-3(L)(2)(BIME)(H2O)(2)] (4), [Pb-7(L)(4)(mu(3)-OH)(2)(H2O)(2)]center dot 8H(2)O (5), [Zn-4(L)(2)(BET)(mu(4)-O)] (6), [Zn-2(HL)(2)(PBIB)]center dot 2H(2)O (7), and [Zn-3(L)(2)(PBIB)(2)]center dot 4H(2)O (8) (H3L = (3,5-dicarboxylphenyl)-(4-(2'-carboxylphenyl) benzyl) ether, TEA = triethylamine, BIME = 1,2-bis(imidazol-1-yl)ethane, BET = 1,2-bis(1,2,4-triazole-1-yl) ethane, and PBIB = 1,4-bis(imidazol-1-ylmethyl)benzene) have been synthesized under hydrothermal conditions. Compound 1 exhibits a three-dimensional (3D) (3,12)-connected framework based on decanuclear [Zn-10(mu(3)-OH)(10)(COO)(12)] units. Compound 2 displays a 3D (3,6)-connected framework based on trinuclear [Zn-3(mu(3)-OH)(CO2)(6)] units. Compounds 3 and 4 display unusual 2-fold interpenetrated 3D (3,6)-connected frameworks with the same (4(2).6)(2)(4(4).6(2).8(8).10) topology. Compound 5 features a 3D tetranodal (3,3,4,8)-connected framework based on pentanuclear [Pb-5(COO)(8)(mu(3)-OH)(2)(H2O)(2)] units. Compound 6 exhibits an unprecedented 2D (3,8)-connected network with (3.4(2))(4(6).5(7).6(8).7(3).8) topology based on tetranuclear [Zn-4(mu(4)-O)(COO)(6)] units. Compound 7 reveals a wavy 2D sheet with (4(4).6(2)) topology. Further, each sheet is interdigitated by two others in a parallel fashion to yield an unusual 2D -> 3D interdigitated framework. Compound 8 displays a 3D rare trinodal (3,4,6)-connected framework with (3.4.5)(2)(3(2).10(3).11)(3(2).4(2).5(2).10(3).11(4).12.13) topology. These compounds have been characterized by IR spectra, UV-vis spectra, TGA, and powder XRD patterns. The optical band gaps and photoluminescent behaviors of 1-8 have been investigated in detail. In addition, surface photovoltage spectroscopies of compounds 1-4 indicate that these compounds possess positive surface photovoltage (SPV) responses in the range of 300-600 nm.